(1) Field of the Invention
This invention relates to a four-way switching valve, and more particularly to a four-way switching valve which carries out switching of refrigerant lines e.g. in a heat pump-type heating and cooling system for an automotive vehicle when the system is switched between a cooling operation mode and a heating operation mode.
(2) Description of the Related Art
In a heating and cooling system for an automotive vehicle, a refrigeration cycle is employed when cooling operation is performed, and when heating operation is performed, engine coolant is used as a heat source. Recently, however, due to the improvement in combustion efficiency of the engine, the temperature of the coolant does not rise high enough to obtain sufficient heating temperature in winter. For this reason, there is an increasing need for a system which can perform both cooling and heating. In a heating and cooling system of this kind, it is necessary to reverse the direction of flow of refrigerant flowing through an indoor heat exchanger and an outdoor heat exchanger, as the system is switched between cooling and heating operations. It is a four-way switching valve that switches the direction of flow of the refrigerant.
FIG. 17 is a block diagram showing the arrangement of a heating and cooling system using the four-way switching valve.
The heating and cooling system is comprised of a compressor 101, a four-way switching valve 102, an outdoor heat exchanger 103, a pressure-reducing device 104, an indoor heat exchanger 105, and an accumulator 106. The four-way switching valve 102 has four ports A to D. The port A of the four-way switching valve 102 is connected to a delivery side of the compressor 101, the port B is connected to the outdoor heat exchanger 103, the port C is connected to the indoor heat exchanger 105, and the port D is connected to the accumulator 106.
During cooling operation, the four-way switching valve 102 is switched such that the port A and the port B are communicated with each other and the port C and the port D are communicated with each other, as indicated by solid lines in FIG. 17. Therefore, a high-temperature and high-pressure refrigerant compressed by the compressor 101 flows into the port A of the four-way switching valve 102, and is sent from the port B to the outdoor heat exchanger 103, where the refrigerant is caused to undergo heat exchange and condensed, and then adiabatically expanded to a low-temperature and low-pressure refrigerant by the pressure-reducing device 104. The indoor heat exchanger 105 causes the low-temperature and low-pressure refrigerant to exchange heat with warm air in the compartment and evaporate. Then, the refrigerant flows through the port C and the port D of the four-way switching valve 102 to enter the accumulator 106, where the refrigerant is separated into gas and liquid, followed by returning to the compressor 101.
On the other hand, during heating operation, the four-way switching valve 102 is switched such that the port A and the port C are communicated with each other and the port B and the port D are communicated with each other, as indicated by broken lines in the figure. Therefore, the high-temperature and high-pressure refrigerant compressed by the compressor 101 flows through the port A and the port C of the four-way switching valve 102, to enter the indoor heat exchanger 105, where the refrigerant exchanges heat with cool air in the compartment to heat the same. The refrigerant condensed by the indoor heat exchanger 105 is adiabatically expanded to the low-temperature and low-pressure refrigerant by the pressure-reducing device 104. Then, the refrigerant undergoes heat exchange at the outdoor heat exchanger 103 to evaporate, and then passes through the port B and the port D of the four-way switching valve 102 to flow into the accumulator 106, where the refrigerant is separated into gas and liquid, followed by returning to the compressor 101.
As described above, the four-way switching valve 102 can switch the operation mode of the heating and cooling system, by switching the flow path of refrigerant.
As the four-way switching valve 102, there is one proposed in Japanese Patent Application No. 2001-183291 by the present applicant. This four-way switching valve is configured such that a first valve and a third valve for opening and closing passages from a port A into which a high-pressure refrigerant is introduced, to a port B or a port C, and a second valve and a fourth valve for opening and closing passages from the port B or the port C to a low-pressure port D are made separate and independent, and that the first valve and the second valve, and the third valve and the fourth valve are actuated by a first piston and a second piston, respectively. It is also configured such that two solenoid valves are provided for selectively guiding part of the high-pressure refrigerant introduced into the port A, to pressure chambers for the first and second pistons.
This enables the two solenoid valves to guide the high-pressure fluid from the port A into the pressure chamber for the first piston or that for the second piston in a switching manner, thereby making it possible to switch between a first state in which the port A is communicated with the port B, and the port C is communicated with the port D, and a second state in which the port A is communicated with the port C, and the port B is communicated with the port D.
However, due to the construction of the conventional four-way switching valve in which two sets of three-way switching valves are arranged in parallel with each other within a body, the body is increased in size, and further due to necessity of machining two sets of valve elements, and cylinders for receiving pistons for driving the valve elements, the manufacturing costs are increased.
The present invention has been made in view of these points, and an object thereof is to provide a four-way switching valve which is compact in size and inexpensive.
To achieve the object, there is provided a four-way switching valve for switching between a first state in which a fluid introduced into a first port is guided to a second port to allow the same to flow out therefrom and the fluid introduced into a third port is guided to a fourth port to allow the same to flow out therefrom, and a second state in which the fluid introduced into the first port is guided to the third port to allow the same to flow out therefrom and the fluid introduced into the second port is guided to the fourth port to allow the same to flow out therefrom. The four-way switching valve comprises a first three-way switching valve for carrying out a switching operation to cause the second port to communicate with the first port or the fourth port, a second three-way switching valve for carrying out a switching operation in unison with the first three-way switching valve to cause the third port to communicate with the fourth port or the first port, and a piston for simultaneously actuating a valve element of the first three-way switching valve and a valve element of the second three-way switching valve, the first three-way switching valve, the second three-way switching valve, and the piston being coaxially arranged within a hollow cylindrical body, wherein the first three-way switching valve and the second three-way switching valve each comprises the valve element axially slidably arranged on a driving rod axially arranged, for opening and closing valve holes formed at openings of passages which are arranged on axially both sides of the valve element and communicated with the first port and the fourth port, guides each fixed to the driving rod and axially protruding outward from axially opposite seating surfaces of the valve element via which the valve element is seated, for being inserted into the valve hole to close the valve hole before the valve element is seated, and at the same time for limiting an axially slidable range of the valve element, and a spring for urging the valve elements in such a direction that the valve element is brought into abutment with an axially outwardly arranged one of the guides.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.